Metabolic clearance rate of radioiodinated human growth hormone in man.

The nature of the disappearance of radioiodinated human growth hormone (HGH) from plasma has been reexamined. The metabolic clearance rate (MCR) was determined both from single injection and constant infusion studies. After single injection of highly purified radioiodinated HGH, the disappearance curve remained multiexponential during the period of study (4 hr). The shape of the curve was independent of the growth hormone preparation used. Similar disappearance curves were obtained with unlabeled HGH.MCR values calculated from constant infusion studies were 203 +/-7.8 liters/day per m(2) and values derived from single injection studies agreed closely with this. The multiexponential nature of the disappearance curve does not permit meaningful calculation of volume of distribution or half-time of disappearance.